1215665121 has 16 divisors (see below), whose sum is σ = 1872255168. Its totient is φ = 693427200.

The previous prime is 1215665111. The next prime is 1215665159.

1215665121 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 1215665121 - 2⁷ = 1215664993 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1215665111) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1082920 + ... + 1084041.

It is an arithmetic number, because the mean of its divisors is an integer number (117015948).

Almost surely, 2^1215665121 is an apocalyptic number.

1215665121 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1215665121 is a deficient number, since it is larger than the sum of its proper divisors (656590047).

1215665121 is a wasteful number, since it uses less digits than its factorization.

1215665121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2166992.

The product of its digits is 3600, while the sum is 30.

The square root of 1215665121 is about 34866.3895607217. The cubic root of 1215665121 is about 1067.2626689495.

It can be divided in two parts, 12156 and 65121, that added together give a palindrome (77277).

The spelling of 1215665121 in words is "one billion, two hundred fifteen million, six hundred sixty-five thousand, one hundred twenty-one".